From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-5.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id A661DC2D0E4 for ; Tue, 17 Nov 2020 14:20:24 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 5E00A221F8 for ; Tue, 17 Nov 2020 14:20:24 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728442AbgKQOUX (ORCPT ); Tue, 17 Nov 2020 09:20:23 -0500 Received: from gentwo.org ([3.19.106.255]:36714 "EHLO gentwo.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725355AbgKQOUX (ORCPT ); Tue, 17 Nov 2020 09:20:23 -0500 Received: by gentwo.org (Postfix, from userid 1002) id 6A0B63F4C9; Tue, 17 Nov 2020 14:20:22 +0000 (UTC) Received: from localhost (localhost [127.0.0.1]) by gentwo.org (Postfix) with ESMTP id 694F13F1C3; Tue, 17 Nov 2020 14:20:22 +0000 (UTC) Date: Tue, 17 Nov 2020 14:20:22 +0000 (UTC) From: Christopher Lameter X-X-Sender: cl@www.lameter.com To: Jens Domke cc: linux-rdma@vger.kernel.org Subject: Re: Is there a working cache for path record and lids etc for librdmacm? In-Reply-To: Message-ID: References: User-Agent: Alpine 2.22 (DEB 394 2020-01-19) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Precedence: bulk List-ID: X-Mailing-List: linux-rdma@vger.kernel.org On Tue, 17 Nov 2020, Jens Domke wrote: > I have used ibacm successfully years ago (think somewhere in the > 2013-2015 timeframe) but abandoned the approach because some > measurements indicated that using OpenMPI with rdmacm had a big > runtime overhead compared to using OpenMPI+oob (Mellanox was > informed but I'm unsure how much has changed until now) Mellanox does not support ibacm.... But ok. Thanks. Good to know someone that has actually used it. > > Is there something that can locally cache the results of the SM queries to > > avoid additional requests? > > Not that I know of, but others might know better. Maybe try contacting > Sean Hefty (driver behind ibacm) directly if he missed your email here > on the list. I have talked to Ira Weiny who wax the last one who did major changes to the source but he does not know of any alternate solution. > > We have tried IBACM but the address resolution does not work on it. It is > > unable to complete a request for any address resolution and leaves kernel > > threads that never terminate instead. > > Setting up ibacm was/is painful, maybe you could verify that it works on > a test bed with lowlevel rdmacm tools to debug with ping-pong, etc. That was done and the bug was confirmed. There is bitrot there in the MAD communication layer. > Furthermore, another thing I learned the hard way was that a cold cache > can overwhelm opensm as well. So, if you deploy ibacm, you have to make > sure that not too many requests go to the local ibacm on too many nodes > simultaneously right after starting ibacm service, otherwise having all > nodes sending numerous requests to opensm could timeout -> could be the > reason for your stalled kernel threads. Right But our cluster only has around 200 nodes max. Should be fine. > (another explanation is obviously a bug in ibacm and/or incompatibility > to newer versions of librdmacm or opensm or other IB libs) > > Sorry, that I cannot provide more specific and direct help, but maybe my > pointers can help you solve the issue. Thanks.